Marches of Wales

The Welsh Marches (Welsh: Y Mers) is an imprecisely defined area along and around the border between England and Wales in the United Kingdom. The precise meaning of the term has varied at different periods.

Historically, the English term Welsh March (in Medieval Latin Marchia Walliae) was originally used in the Middle Ages to denote the marches between England and the Principality of Wales, in which Marcher lords had specific rights, exercised to some extent independently of the king of England. In modern usage, "the Marches" is often used to describe those English counties which lie along the border with Wales, particularly Shropshire and Herefordshire, and sometimes adjoining areas of Wales.

After the decline and fall of the Roman Empire which occupied Britain until about AD 410, the area which is now Wales comprised a number of separate Romano-British kingdoms, including Powys in the east. Over the next few centuries, the Angles, Saxons and others gradually conquered and settled in eastern and southern Britain. The kingdom of Mercia, under Penda, became established around Lichfield, and initially established strong alliances with the Welsh kings. However, his successors sought to expand Mercia further westwards into what is now Cheshire, Shropshire and Herefordshire. Campaigns and raids from Powys then led, possibly around about AD 820, to the building of Wat's Dyke, a boundary earthwork extending from the Severn valley near Oswestry to the Dee estuary. As the power of Mercia grew, a string of garrisoned market towns such as Shrewsbury and Hereford defined the borderlands as much as Offa's Dyke, a stronger and longer boundary earthwork erected by order of Offa of Mercia between AD 757 and 796. The Dyke still exists, and can best be seen at Knighton, close to the modern border between England and Wales.

...
Wikipedia